1. Field of the Invention
This invention relates to a telephone set having both the function of recognizing the telephone number of a caller and the function of calling back the caller.
2. Description of the Prior Art
Some of telephone sets have the following additional functions. In cases where a telephone set is called, the telephone set recognizes the telephone number of the caller before answering the call. This function of the telephone set uses such services offered by an exchange that the exchange transmits data of the telephone number of the caller to the called party together with a call incoming signal. The telephone set has a memory for storing the telephone number of the caller. During the absence of the user of the telephone set, when the telephone set is called, the memory stores the telephone number of the caller. After the end of the absence, the user can call back the caller by referring to the caller telephone number stored in the memory.
According to caller telephone number transmission services (caller ID services) in the United States, caller telephone number data transmitted from an exchange contains an area code. In cases where the caller and the called party are in a same area, the area code needs to be deleted when the called party executes the call back process. In some cases, "1" needs to be appended to the head of the telephone number of the caller when the called party executes the call back process. Thus, editing the telephone number of the caller which is read out from the memory is actually executed in the called party.
According to a prior art method of editing the telephone number of the caller, digits of the telephone number sequence are erased, changed, or added one by one. Therefore, the prior art method tends to be complicated, and editing the telephone number usually spends a long time.